Regulator circuit, corresponding system and method

ABSTRACT

A circuit includes an electronic switch configured to be coupled intermediate a high-voltage node and low-voltage circuitry and configured to couple the low-voltage circuitry to the high-voltage node. A voltage-sensing node is configured to be coupled to the high-voltage node via a pull-up resistor. A further electronic switch can be switched to a conductive state to couple the voltage-sensing node and the control node of the electronic switch. A comparator compares a threshold with a voltage at the voltage-sensing node and causes the further electronic switch to switch on in response to the voltage at said voltage-sensing node reaching said threshold. A charge pump coupled to the current flow-path of the electronic switch is activated to the conductive state to pump electric charge from the current flow-path of the electronic switch to the control node of the electronic switch via the further electronic switch switched to the conductive state.

BACKGROUND Technical Field

The description relates to regulator circuits.

One or more embodiments can be applied to driving bypass field-effecttransistors in high-voltage startup regulators as used in a variety ofproducts.

These products may include, for instance, chargers/adapters, homeappliances such as refrigerators or TVs, industrial machinery, telecomapparatus and so on.

Description of the Related Art

Regulator circuits such as high-voltage startup (HVS) regulators mayinclude a bypass transistor (a MOSFET transistor, for instance), apull-up resistor used to bias the gate of the bypass transistor, as wellas a voltage clamp connected between the gate of the bypass transistorand ground in order to limit the gate voltage range and define a maximumsupply voltage output.

Such an approach may exhibit certain limitations in terms of powerconsumption, application input range, and cost.

For instance, in low-power applications, a constraint may be placed onthe lowest (minimum) resistance value for the pull-up resistor.

Under those circumstances, achieving a trade-off between such aconstraint on the minimum resistance value for the pull-up resistor andthe lowest (minimum) high-voltage input may become critical, while onthe other hand a bypass component with a gate bias current stillrepresents an attractive, cost-effective solution.

BRIEF SUMMARY

One or more embodiments of the present disclosure contribute inaddressing the issues discussed in the foregoing.

According to one or more embodiments, such technical features orbenefits can be achieved by a circuit as will be described in furtherdetail herein.

One or more embodiments may relate to a corresponding system. Aswitched-mode power supply (SMPS) system may be exemplary of such asystem.

One or more embodiments may relate to a corresponding method.

One or more embodiments may provide a cost-effective solution, primarilyin comparison with the use of a dedicated HV-MOS with no gate leakage.

One or more embodiments may use a charge pump to sustain the gateleakage current. Such a charge pump can be supplied by a transistorsource and its activation may thus involve pulling-up the gate of thebypass transistor.

In one or more embodiments, an (electronic) switch may be interposedbetween the gate and the pull-up resistor.

The switch can be closed (that is, made conductive) by a latchedcomparator in response to the input voltage reaching (that is, rising upto) a comparator threshold.

The charge stored in a capacitor intermediate (between) the pull-upresistor (RHV) and ground facilitates pulling-up the gate with thecapability of providing both supply energy as consumed by thecomparator/latch and supporting gate leakage, before charge pumpturn-on.

One or more embodiments can effectively address certain limitations interms of power consumption, application input range, and cost.

The possible presence of an embedded charge pump may result in anegative current detected on a high-voltage pin when the high voltagestartup regulator is active.

In at least one embodiment, a circuit is provided that includes a firstelectronic switch having a current flow path therethrough. The firstelectronic switch is configured to be coupled between a high-voltagenode and low-voltage circuitry. The first electronic switch has acontrol node configured to switch the first electronic switch to aconductive state in which the first electronic switch electricallycouples the low-voltage circuitry to the high-voltage node. Avoltage-sensing node is configured to be coupled to the high-voltagenode via a pull-up resistor. A second electronic switch is coupledbetween the voltage-sensing node and the control node of the firstelectronic switch. The second electronic switch is switchable to aconductive state in which the second electronic switch electricallycouples the voltage-sensing node to the control node of the firstelectronic switch in response to receiving a switch-on signal. Acomparator is coupled to the voltage-sensing node and a threshold. Thecomparator is configured to compare a voltage at the voltage-sensingnode with the threshold and generate the switch-on signal in response tothe voltage at the voltage-sensing node reaching the threshold. A chargepump is coupled to the current flow-path of the first electronic switchand configured to be activated with the second electronic switchswitched to the conductive state to pump electric charge from thecurrent flow-path of the first electronic switch to the control node ofthe first electronic switch via the second electronic switch switched tothe conductive state.

In at least one embodiment, a power supply system is provided thatincludes a high-voltage source, low-voltage circuitry, and a circuit.The circuit includes a high-voltage node coupled to the high-voltagesource. A first electronic switch has a current flow path therethrough,and the first electronic switch is coupled between the high-voltage nodeand low-voltage circuitry. The first electronic switch has a controlnode configured to switch the first electronic switch to a conductivestate in which the first electronic switch electrically couple thelow-voltage circuitry to the high-voltage node. A pull-up resistor iscoupled between a voltage-sensing node and the high-voltage node. Asecond electronic switch is coupled between the voltage-sensing node andthe control node of the first electronic switch, and the secondelectronic switch is switchable to a conductive state in which thesecond electronic switch electrically couples the voltage-sensing nodeto the control node of the first electronic switch in response toreceiving a switch-on signal. A comparator is coupled to thevoltage-sensing node and a threshold, and the comparator is configuredto compare a voltage at the voltage-sensing node with the threshold andgenerate the switch-on signal in response to the voltage at saidvoltage-sensing node reaching said threshold. A charge pump is coupledto the current flow-path of the first electronic switch and configuredto be activated with the second electronic switch switched to theconductive state to pump electric charge from the current flow-path ofthe first electronic switch to the control node of the first electronicswitch via the second electronic switch switched to the conductivestate.

In at least one embodiment, a method is provided that includes: couplinga first electronic switch between a high-voltage source and low-voltagecircuitry, the first electronic switch having a current flow paththerethrough and a control node; electrically coupling the low-voltagecircuitry to the high-voltage source by switching the first electronicswitch to a conductive state via the control node; coupling avoltage-sensing node to the high-voltage source via a pull-up resistor;coupling a second electronic switch between the voltage-sensing node andthe control node of the first electronic switch; coupling thevoltage-sensing node to the control node of the first electronic switchby switching the second electronic switch to a conductive state inresponse to the voltage at said voltage-sensing node reaching athreshold; coupling a charge pump to the current flow-path of the firstelectronic switch; and activating the charge pump with the secondelectronic switch switched to the conductive state to pump electriccharge from the current flow-path of the first electronic switch to thecontrol node of the first electronic switch via the second electronicswitch switched to the conductive state.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more embodiments will now be described, by way of example only,with reference to the annexed figures, wherein:

FIG. 1 is a block diagram exemplary of a high-voltage startup (HVS)regulator;

FIG. 2 is a block diagram of a high-voltage startup (HVS) regulatoraccording to one or more embodiments of the present disclosure;

FIGS. 3A and 3B are block diagrams illustrating operation of a regulatoras illustrated in FIG. 2 ;

FIG. 4 is a transistor-level representation of one or more embodimentsof the present disclosure;

FIG. 5 is a circuit diagram illustrating implementation of a component(charge pump) illustrated in FIG. 4 , in accordance with one or moreembodiments;

FIG. 6 is a set of time diagram illustrative of time behavior ofparticular signals which may occur in a regulator according to one ormore embodiments; and

FIG. 7 is a circuit diagram illustrating use of a regulator according toone or more embodiments within the framework of a switched-mode powersupply system.

DETAILED DESCRIPTION

In the ensuing description one or more specific details are illustrated,aimed at providing an in-depth understanding of examples of embodimentsof this description. The embodiments may be obtained without one or moreof the specific details, or with other methods, components, materials,etc. In other cases, known structures, materials, or operations are notillustrated or described in detail so that certain aspects ofembodiments will not be obscured.

Reference to “an embodiment” or “one embodiment” in the framework of thepresent description is intended to indicate that a particularconfiguration, structure, or characteristic described in relation to theembodiment is comprised in at least one embodiment. Hence, phrases suchas “in an embodiment” or “in one embodiment” that may be present in oneor more points of the present description do not necessarily refer toone and the same embodiment.

Moreover, particular conformations, structures, or characteristics maybe combined in any adequate way in one or more embodiments.

The headings/references used herein are provided merely for convenienceand hence do not define the extent of protection or the scope of theembodiments.

By way of introduction to the instant detailed description, referencemay be had to FIG. 1 , which reproduces a circuit diagram of aconventional high-voltage startup (HVS) regulator designated 10 as awhole.

Such a regulator is intended to provide a low voltage supply to alow-voltage section LV from a high voltage source VHVIN. It is notedthat in various types of high-voltage power converters, such ahigh-voltage startup regulator may be used only during a power-on phaseto be subsequently replaced by a more efficient supply source.

A high-voltage startup regulator 10 as illustrated in FIG. 1 comprises a“bypass” electronic switch MBP (a MOSFET transistor, for instance) ableto withstand a high voltage applied across it.

In that respect, those of skill in the art will appreciate that a MOSFETtransistor is referred to herein as the switch MBP merely by way ofexample: other types of electronic switches (for instance, JFET, BJT,GaN) may be used as the switch MBP.

As illustrated in FIG. 1 , the switch MBP is arranged with the currentpath therethrough (source-drain, in the case of a field-effecttransistor such as a MOSFET) coupled intermediate an input node to whicha high voltage VHVIN can be applied and the low-voltage section LV,which can be assumed to be referred to ground GND.

As illustrated in FIG. 1 , the drain D of the MOSFET transistor MBP isconnected to the high-voltage input node at VHVIN while the source S ofthe MOSFET transistor MBP supplies the low-voltage circuitry LV.

A pull-up resistor RHV is used to bias the control node G (gate, in thecase of a field-effect transistor such as a MOSFET) of the bypass switchMBP.

As illustrated, the pull-up resistor RHV is arranged between thehigh-voltage input node at VHVIN and the gate G of MBP.

A voltage clamp DZ (a Zener diode, for instance) is arranged between thegate G of MBP and ground GND in order to limit the gate voltage range ofMBP and define a highest (maximum) supply voltage for the low-voltagesection LV.

In order to reach this voltage value, the input voltage is selectedabove the DZ voltage clamp.

In low-power applications, a constraint on the minimum value of theresistance of RHV is set in order to limit waste of power. Anotherspecification is the lowest (minimum) input voltage (VHVIN_(MIN)) forwhich the high-voltage regulator is expected to be capable of supplyingthe downstream circuits.

Assuming MBP is a component having a gate bias current (I_(GATE)) acertain voltage drop on RHV may exist which establishes a judicioustrade-off between the constraint on the minimum RHV and the minimumhigh-voltage input.

A problem arises when this trade-off cannot be satisfactorily reached.

For instance, with RHV=10 MSΩ and I_(GATE)=101 μA, the minimum inputvoltage is above 100V.

In principle, using a lower resistance value for RHV may be considered,to the point of even dispensing with such resistance. It is otherwisenoted that the minimum value for that resistance is related to adesirably reduced stand-by consumption, which results in a designconstraint.

Also, using a component “with leakage” may be an attractive option inmonolithic or System in Package (SiP) arrangements: for instance, ahigh-voltage component with non-zero gate current may represent the onlycomponent available in a certain technological process and/or mayrepresent an advantageous choice in view of specific designcharacteristics.

For instance, gallium-nitride (GaN) technology may be selected for themain switch in a converter in view of its improved static and dynamicperformance in comparison with silicon-based power MOS transistors.Adding a dedicated component (a SIP with a dedicated die and/or process)may be more expensive and complex.

Using a bypass component MBP with a gate bias current I_(GATE) forced toflow through RHV and then into the gate of MBP may provide a solutionwhich is cost-effective and attractive (for instance, resulting in amonolithic solution with only one component available). Such an approachmay otherwise exhibit various drawbacks: for instance, it may be hardlysuited for use in very-low standby applications and/or may end up byproviding undesirably expensive and complex solutions.

One or more embodiments may address these issues adopting the approachillustrated in FIG. 2 .

In that respect, it will be appreciated that:

-   -   unless the context indicates otherwise, like parts or elements        are indicated throughout the annexed figures with like reference        symbols, and a detailed description will not be repeated for        each and every figure for brevity; consequently, parts or        elements already discussed in connection with FIG. 1 are        indicated throughout the annexed figures with like reference        symbols and will not be not discussed again;    -   for the sake of simplicity and ease of understanding, a same        designation may be used herein to indicate both a node or line        in a circuit and a signal (voltage, current, for instance)        occurring at that node or line: see, for instance, VHVIN, as        already introduced previously;    -   various components illustrated and discussed for ease of        explanation (the source of the high-voltage VHVIN and the        low-voltage circuitry LV, for instance) may be distinct elements        from the embodiments.

In one or more embodiments as illustrated in FIG. 2 , circuitrydesignated 100 as a whole is coupled intermediate:

-   -   a node HV intermediate the resistor RHV and the voltage clamp        DZ, and the control node G (here, gate) of the switch MBP.

As illustrated, the circuitry 100 comprises an electronic switch SW1 (aMOSFET transistor, for instance) with the current path therethrough(source-drain, in the case of a field-effect transistor such as aMOSFET) configured to connect—in response to the switch SW1 being “on”,that is, conductive—the control node G of the “main” switch MBP to thenode HV, and thus to the pull-up resistor RHV.

As illustrated, the circuitry 100 also comprises:

-   -   a capacitor CHV interposed between the node HV and ground (that        is, in parallel to the voltage clamp DZ;    -   a comparator 102 configured to sense the voltage at the node HV        (that is, the voltage across the capacitor CHV) with a threshold        VTH (generated in a manner known per se to those of skill in the        art);    -   a latch circuit 104 configured to latch the output of the        comparator 102 and to control via its output the status of the        switch SW1; and    -   a charge pump 106 interposed between a node S (source, for        instance, in the case of a field-effect transistor such as        MOSFET) intermediate the switch MBP and the low-voltage section        LV and the node HV, the charge pump 106 having the purpose of        sustaining a bias current through the switch MBP while avoiding        an undesired voltage drop on RHV.

FIGS. 3A and 3B are exemplary of possible operation of a regulator 10 asexemplified in FIG. 2 .

Once again, unless the context indicates otherwise, parts or elementsalready discussed in connection with FIGS. 1 and 2 are indicated inFIGS. 3A and 3B with like reference symbols and will not be notdescribed again for brevity.

More specifically, FIGS. 3A and 3B are exemplary of possible currentflows in a regulator 10 as per the embodiments exemplified in FIG. 2 :

-   -   before the charge pump 106 is turned on (FIG. 3A),    -   after the charge pump 106 is turned on (FIG. 3B).

At power-on, SW1 is assumed to be open (non-conductive) and no currentI_(GATE) can flow through RHV towards the node G and the voltage at thenode HV follows VHVIN.

In response to the voltage at the node HV reaching the threshold VTH ofthe comparator 102 (20 V, by way of example), the related information isstored by the latch 104 and SW1 is closed (that is, made conductive) viaa signal SW1_ON being asserted.

In this phase the charging of the capacitor CHV is used to pull-up thegate G of the switch MBP (exploiting the intrinsic gate-sourcecapacitance, for instance) and a current I_(GATE) is provided towardsthe node G.

When the voltage on the source S of MBP is enough (that is, it exceeds alower threshold as desired), the charge pump 106 starts to supplycurrent towards the node HV, drawing current from the source S of MBP(see FIG. 3B).

The charge pump 106 thus provides the current I_(GATE) and a current inexcess of I_(GATE) used to charge the capacitor CHV up to the voltageclamp of HV.

That is, during high-voltage regulator operation, the resistor RHV doesnot contribute appreciably to supplying the current I_(GATE) and thevoltage drop across RHV does not limit the lowest (minimum) inputvoltage, which is independent both of the resistance value of RHV valueand of the intensity of I_(GATE).

FIG. 4 is a transistor-level diagram exemplary of a of a possibleembodiment of the layout illustrated in FIG. 2 based on a latchedcurrent comparator 1024, which is configured to facilitate having acurrent IHVtrig through the resistor RHV such that IHVtrig<<<I_(GATE).

Once again, unless the context indicates otherwise, parts or elementsalready discussed in connection with FIGS. 1, 2 and 3A and 3B areindicated in FIG. 4 with like reference symbols and will not be notdescribed again for brevity.

Essentially, the latched comparator 1024 is based on a current mirror M3including two transistors Q1 (in a diode-like configuration) and Q2having current flow paths therethrough (emitter-collector, in the caseof bipolar transistors as exemplified herein) that define respectivecurrent flow lines:

between the node HV and ground GND via the current clamp DZ (transistorQ1), and between the control node (gate) of the switch SW1 and groundGND (transistor Q2).

The mutually connected bases of the transistors Q1 and Q2 are coupled tothe node HV via the current flow path (source-drain, in the case of aMOSFET transistor as exemplified herein) through a further electronicswitch M1 whose control node (gate in the case of a MOSFET transistor asexemplified herein) is coupled to the control node of the switch SW1 viethe line where the switching signal SW1_ON is applied with the parallelconnection of a further voltage clamp DZUP and further pull-up resistorRup coupling that line with the line/node HV.

In FIG. 4 , the main currents before start-up are indicated incontinuous lines. Dashes lines denote main currents at startup and chainlines denote the main currents in steady state after activation of thecharge pump 106.

The charge pump 106 can be of any conventional type, such as Dickson,for instance, as exemplified in FIG. 5 .

FIG. 6 comprises a set time diagrams exemplary of possible timebehaviors, mapped against a common time (abscissa) scale of thefollowing signals:

-   -   the “high” voltage VHVIN (continuous line)    -   the signal SW1_ON (dashed line)    -   the voltage at node HV (chain line)    -   the voltage at node G (mixed dash and cross line--+--+, which        finally superposes with the voltage at node HV    -   the voltage S ((mixed dash and double-cross line--++--++--.

The diagrams of FIG. 6 are exemplary of a possible start-up sequenceincluding events designated with numbers from 1 to 5 such as:

-   -   1—the node HV reaches the threshold VTH that triggers the        closing of SW1 (at a time tstart);    -   2—the intrinsic capacitance at the node G is charged via charge        sharing with the capacitance CHV;    -   3—charge sharing causes a voltage drop on the node HV until the        voltage at that node equals the voltage on the G node (at a time        tcharge after tstart);    -   4—the S node follows the node G with a voltage drop therebetween        close to the threshold of MBP and MBP starts supplying the        charge pump 106 (time tstartCHP);    -   the charge pump 106 re-charges the capacitor CHV up to the        voltage clamp.

FIG. 7 is a circuit diagram exemplary of the possible use of circuit 10as discussed in the foregoing within the framework of a switched-modepower supply (that is an electronic power supply system thatincorporates a switching regulator to convert electrical powerefficiently).

Once again, unless the context indicates otherwise, parts or elementsalready discussed in connection with the previous figures are indicatedin FIG. 7 with like reference symbols and will not be not describedagain for brevity.

FIG. 7 illustrates the possible use of embodiments in connection with asystem in package (SIP) switched-mode power supply controller generallydesignated SMPS.

FIG. 7 exemplifies the possible use of embodiments in switching powercontrollers (with a flyback topology in the—purely exemplary—caseillustrated) integrating a main power switch PM (a power MOSFETtransistor, for instance), with part of the circuit 10 included in thecontroller (for instance the clamp DZ, the bypass FET driver 100, andthe switch MBP) while other components (such as the resistor RHV) may beexternal parts distinct from the circuit 100 (and 10).

For instance, this may be the case of the source of the high-voltageVHVIN, represented in FIG. 7 by a bridge rectifier BR supplied by an ACsource ACin (a mains distribution grid, for instance) and havingassociated therewith a smoothing capacitor Cin intended to be coupledwith the line or node VHVIN.

In an arrangement as exemplified in FIG. 7 , in the place of beingcoupled to VHVIN directly as discussed previously, the switch MBP iscoupled to VHVIN (at its drain) indirectly, that is, via the primarywinding of the converter transformer T.

In an arrangement as exemplified in FIG. 7 , the low-voltage circuitryLV coupled to the switch MBP (here at the source) includes the supplyportion of the SMPS controller, including a supply node VDD.

The external network coupled to the node VDD is exemplified as a windingdriving a rectifier diode and a smoothing capacitor Cvdd (not to beconfused with the capacitor CHV discussed previously), provides anauxiliary power supply active during regulation. A current generatorIcharge is illustrated as exemplary of the node VDD being charged with acontrolled current. The current generator could be replaced with a diodeexemplary of the fact that the auxiliary power supply and the powersupply from the HVS circuit are mutually decoupled.

The symbol PM in FIG. 7 denotes a main switch of the switchingconverter. Advantageously, this may be of the same type of switch MBP (aGaN transistor, for instance).

The reference 108 in FIG. 7 denotes the logic control circuitry of theswitch PM, which applies to the switch a PWM-modulated control signalvia a driver 110.

This may occur in any conventional manner known to those of skill in theart. It will be otherwise appreciated that FIG. 7 provides a fairlygeneral representation of a switching controller: reference to a SMPSconverter controller as made in FIG. 7 is thus merely exemplary and notlimiting of the embodiments.

One or more embodiments may in fact be applied to flyback, boosttopologies and other types of bypass regulators as a high-voltagestartup current generator.

One or more embodiments may provide various advantages such as, forinstance:

-   -   power consumption is reduced,    -   limits on the application input range are removed,    -   a cost-effective solution is provided in comparison with the use        of dedicated HV-MOS that has no gate leakage,    -   gate leakage current flowing in the resistor RHV at power-on is        avoided via the switch SW1,    -   the comparator and latch circuitry (that is 102, 104, 1024)        exhibits a low consumption before the switch SW1 is turned-on,    -   a simple charge pump circuit is used to sustain bypass FET gate        leakage.

Briefly, one or more embodiments remove a limitation of conventionalhigh-voltage startup regulators employing as a bypass component anelectronic switch having a (high) bias current.

In that respect, it is again noted that, while a MOSFET transistor hasbeen referred throughout as exemplary of the switch MBP, other types ofelectronic switches (for instance, JFET, BJT, GaN) may be used for thesame purposes.

Such a limitation is related to the voltage drop on a pull-up resistor(RHV, for instance) having one end used to bias the bypass switch gatesuch a resistor and other end connected at the main input voltage.

One or more embodiments use a charge pump in order sustain the gateleakage current.

Such a charge pump can be supplied by the transistor source and itsactivation involves pulling-up the gate of the bypass switch MBP.

In one or more embodiments an electronic switch SW1 is interposedbetween the control node (gate, for instance) of the bypass switch MBPgate and the pull-up resistor. The switch is closed (by a latchedcomparator, for instance) as soon as the input voltage reaches acomparator threshold.

The charge stored in a capacitor (CHV, for instance) connected betweenRHV and GND facilitates gate pull-up with the capability of supplying(and sustaining) both the consumption of the comparator/latchconsumption and gate leakage, before the charge pump turning-on.

Briefly, a circuit (for instance, 10) as exemplified herein maycomprise:

-   -   an electronic switch (for instance, MBP) having a current flow        path (for instance, S, D) therethrough, the electronic switch        configured to be coupled intermediate a high-voltage node (for        instance, VHVIN) and low-voltage circuitry (for instance, LV),        the electronic switch having a control node (for instance, G)        configured to switch the electronic switch to a conductive state        wherein the low-voltage circuitry is coupled to the high-voltage        node.

A circuit as exemplified herein may further comprise a voltage-sensingnode (for instance, HV) configured to be coupled to the high-voltagenode via a pull-up resistor (for instance, RHV),

-   -   a further electronic switch (for instance, SW1) intermediate the        voltage-sensing node and the control node of the electronic        switch, the further electronic switch switchable to a conductive        state to couple the voltage-sensing node and the control node of        the electronic switch in response to a switch-on signal (for        instance, SW1_ON) being asserted,    -   a comparator (for instance, 102) coupled to the voltage-sensing        node and a threshold, the comparator configured to compare a        voltage at said voltage-sensing node with the threshold and        cause the switch-on signal to be asserted in response to the        voltage at said voltage-sensing node reaching said threshold,        and    -   a charge pump (for instance, 106) coupled to the current        flow-path of the electronic switch and configured to be        activated with the further electronic switch switched to the        conductive state to pump electric charge (for instance,        I_(GATE)) from the current flow-path of the electronic switch to        the control node of the electronic switch via the further        electronic switch switched to the conductive state.

A circuit as exemplified herein may comprise a charge capacitor (forinstance, CHV) coupled (for instance, via HV) to the charge pump to becharged thereby via charge in excess of the charge pumped to the controlnode of the electronic switch.

In a circuit as exemplified herein, the charge pump is coupled to thevoltage-sensing node and configured to pump therein charge sourced fromthe current flow-path of the electronic switch.

A circuit as exemplified herein may comprise a latch circuit (forinstance, 104) intermediate the comparator and the further electronicswitch to latch therein said switch-on signal in response to the voltageat said voltage-sensing node reaching said threshold.

In a circuit as exemplified herein, the voltage-sensing node isconfigured to be coupled to the high-voltage node intermediate saidpull-up resistor (for instance, RHV) and a voltage clamp (for instance,DZ) referred to ground (for instance, GND) configured to clamp to alimit value the voltage at the voltage-sensing node.

In a circuit as exemplified herein, the electronic switch (for instance,MBP) has a first node (for instance, D) configured to be coupled to thehigh-voltage node (for instance, VHVIN) and a second node (for instance,S) configured to be coupled to the low-voltage circuitry (for instance,LV), and wherein the charge pump is coupled to the current flow-path ofthe electronic switch at the second node (for instance, S).

In a circuit as exemplified herein, the electronic switch and thefurther electronic switch may comprise field-effect transistors,optionally MOSFET transistors.

A power supply system as exemplified herein may comprise:

-   -   a high-voltage source (for instance, BR, Cin),    -   a circuit as exemplified herein (for instance, 10) having said        high-voltage node (for instance, VHVIN) coupled to the        high-voltage source (for instance, BR, Cin), and    -   low-voltage circuitry (for instance, LV) coupled (for instance,        at S) to the electronic switch wherein the low-voltage circuitry        is coupled to the high-voltage node in response to the        electronic switch being switched to a conductive state.

A method as exemplified herein may comprise supplying low-voltagecircuitry (for instance, LV) a from a high-voltage source (for instance,BR, Cin) by:

-   -   coupling intermediate the high-voltage source and the        low-voltage circuitry an electronic switch (for instance, MBP)        having a current flow path (for instance, S, D) therethrough and        a control node (for instance, G),    -   switching the electronic switch to a conductive state via the        control node thereof to couple the low-voltage circuitry to the        high-voltage source,    -   coupling a voltage-sensing node to the high-voltage source via a        pull-up resistor (for instance, RHV),    -   providing a further electronic switch (for instance, SW1)        intermediate the voltage-sensing node and the control node of        the electronic switch,    -   switching (for instance, SW1_ON) the further electronic switch        to a conductive state to couple the voltage-sensing node and the        control node of the electronic switch in response to the voltage        at said voltage-sensing node reaching a threshold (for instance,        VTH), and    -   providing a charge pump (for instance, 106) coupled to the        current flow-path of the electronic switch, and    -   activating the charge pump with the further electronic switch        switched to the conductive state to pump electric charge (for        instance, I_(GATE)) from the current flow-path of the electronic        switch to the control node of the electronic switch via the        further electronic switch (SW1) switched to the conductive        state.

Without prejudice to the underlying principles, the details andembodiments may vary, even significantly, with respect to what has beendescribed by way of example only without departing from the extent ofprotection.

A circuit (10) may be summarized as including: an electronic switch(MBP) having a current flow path (S, D) therethrough, the electronicswitch (MBP) configured to be coupled intermediate a high-voltage node(VHVIN) and low-voltage circuitry (LV), the electronic switch (MBP)having a control node (G) configured to switch the electronic switch(MBP) to a conductive state wherein the low-voltage circuitry (LV) iscoupled to the high-voltage node (VHVIN), a voltage-sensing node (HV)configured to be coupled to the high-voltage node (VHVIN) via a pull-upresistor (RHV), a further electronic switch (SW1) intermediate thevoltage-sensing node (HV) and the control node (G) of the electronicswitch (MBP), the further electronic switch (SW1) switchable to aconductive state to couple the voltage-sensing node (HV) and the controlnode (G) of the electronic switch (MBP) in response to a switch-onsignal (SW1_ON) being asserted, a comparator (102) coupled to thevoltage-sensing node (HV) and a threshold (VTH), the comparator (102)configured to compare a voltage at said voltage-sensing node (HV) withthe threshold (VTH) and cause (104) the switch-on signal (SW1_ON) to beasserted in response to the voltage at said voltage-sensing node (HV)reaching said threshold (VTH), and a charge pump (106) coupled to thecurrent flow-path of the electronic switch (MBP) and configured to beactivated with the further electronic switch (SW1) switched to theconductive state to pump electric charge (I_(GATE)) from the currentflow-path of the electronic switch (MBP) to the control node (G) of theelectronic switch (MBP) via the further electronic switch (SW1) switchedto the conductive state.

The circuit (10) may include a charge capacitor (CHV) coupled (HV) tothe charge pump (106) to be charged thereby via charge in excess of thecharge (I_(GATE)) pumped to the control node (G) of the electronicswitch (MBP).

The charge pump (106) may be coupled to the voltage-sensing node (HV)and configured to pump therein charge sourced from the current flow-pathof the electronic switch (MBP).

The circuit (10) may include a latch circuit (104) intermediate thecomparator (102) and the further electronic switch (SW1) to latchtherein said switch-on signal (SW1_ON) in response to the voltage atsaid voltage-sensing node (HV) reaching said threshold (VTH). Thevoltage-sensing node (HV) may be configured to be coupled to thehigh-voltage node (VHVIN) intermediate said pull-up resistor (RHV) and avoltage clamp (DZ) referred to ground (GND) configured to clamp to alimit value the voltage at the voltage-sensing node (HV). The electronicswitch (MBP) may have a first node (D) configured to be coupled to thehigh-voltage node (VHVIN) and a second node (S) configured to be coupledto the low-voltage circuitry (LV), and wherein the charge pump (106) maybe coupled to the current flow-path of the electronic switch (MBP) atthe second node (S). The electronic switch (MBP) and the furtherelectronic switch (SW1) may include field-effect transistors, preferablyMOSFET transistors.

A power supply system may be summarized as including: a high-voltagesource (BR, Cin), a circuit (10) described above having saidhigh-voltage node (VHVIN) coupled to the high-voltage source (BR, Cin),and low-voltage circuitry (LV) coupled (S) to the electronic switch(MBP) wherein the low-voltage circuitry (LV) may be coupled to thehigh-voltage node (VHVIN) in response to the electronic switch (MBP)being switched to a conductive state.

A method of supplying low-voltage circuitry (LV) a from a high-voltagesource (BR, Cin) may be summarized as including: coupling intermediatethe high-voltage source (VHVIN; BR, Cin) and the low-voltage circuitry(LV) an electronic switch (MBP) having a current flow path (S, D)therethrough and a control node (G), switching the electronic switch(MBP) to a conductive state via the control node (G) thereof to couplethe low-voltage circuitry (LV) to the high-voltage source (VHVIN; BR,Cin), coupling a voltage-sensing node (HV) to the high-voltage source(VHVIN; BR, Cin) via a pull-up resistor (RHV), providing a furtherelectronic switch (SW1) intermediate the voltage-sensing node (HV) andthe control node (G) of the electronic switch (MBP), switching (SW1_ON)the further electronic switch (SW1) to a conductive state to couple thevoltage-sensing node (HV) and the control node (G) of the electronicswitch (MBP) in response to the voltage at said voltage-sensing node(HV) reaching a threshold (VTH), and providing a charge pump (106)coupled to the current flow-path of the electronic switch (MBP), andactivating the charge pump (106) with the further electronic switch(SW1) switched to the conductive state to pump electric charge(I_(GATE)) from the current flow-path of the electronic switch (MBP) tothe control node (G) of the electronic switch (MBP) via the furtherelectronic switch (SW1) switched to the conductive state.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A circuit, comprising: a high-voltage node; low-voltage circuitry; afirst electronic switch having a current flow path, the first electronicswitch configured to be coupled between the high-voltage node and thelow-voltage circuitry; a voltage-sensing node coupled to thehigh-voltage node; a second electronic switch coupled between thevoltage-sensing node and the first electronic switch; a comparatorcoupled to the voltage-sensing node; and a charge pump coupled to thecurrent flow path of the first electronic switch.
 2. The circuit ofclaim 1, wherein: the first electronic switch has a control node thatwhen in a conductive state is configured to couple the low-voltagecircuitry to the high-voltage node; the second electronic switch thatwhen in a conductive state is configured to couple the voltage-sensingnode to the control node of the first electronic switch in response. 3.The circuit of claim 2 wherein the second electronic switch isconfigured to receive a switch-on signal and the comparator isconfigured to compare a voltage at the voltage-sensing node with athreshold and generate the switch-on signal in response to the voltageat the voltage-sensing node reaching the threshold.
 4. The circuit ofclaim 3 wherein the charge pump is configured to be activated with thesecond electronic switch when in the conductive state, the charge pumpconfigured to move charge from the current flow path of the firstelectronic switch to the control node of the first electronic switch viathe second electronic switch being in the conductive state.
 5. Thecircuit of claim 4 comprising a charge capacitor coupled to the chargepump, the charge capacitor configured to be charged by the charge pumpvia charge in excess of the charge pumped to the control node of thefirst electronic switch.
 6. The circuit of claim 5, comprising a latchcircuit coupled between the comparator and the second electronic switch,the latch circuit configured to latch the switch-on signal in responseto the voltage reaching the threshold.
 7. The circuit of claim 5,further comprising a voltage clamp coupled between a ground node and thevoltage-sensing node, wherein the voltage clamp is configured to clampto a limit value of the voltage at the voltage-sensing node.
 8. A powersupply system, comprising: a high-voltage source; low-voltage circuitry;and a circuit, including: a first electronic switch coupled between thehigh-voltage source and the low-voltage circuitry; a second electronicswitch coupled between the voltage-sensing node and the first electronicswitch; a comparator coupled to the voltage-sensing node, the comparatorconfigured to compare a voltage at the voltage-sensing node with athreshold and generate a switch-on signal in response to the voltagereaching said the threshold; and a charge pump coupled to the firstelectronic switch and the second electronic switch.
 9. The power supplysystem of claim 8 wherein the charge pump is configured to move chargefrom a current flow path of the first electronic switch to a controlnode of the first electronic switch in response to the second electronicswitch in the conductive state, the system comprising a charge capacitorcoupled to the charge pump, the charge capacitor configured to becharged by the charge pump via charge in excess of the charge pumped tothe control node of the first electronic switch.
 10. The power supplysystem of claim 9, wherein the charge pump is coupled to thevoltage-sensing node and configured to pump charge sourced from thecurrent flow path of the first electronic switch to the voltage-sensingnode.
 11. The power supply system of claim 8, comprising a latch circuitcoupled between the comparator and the second electronic switch, thelatch circuit configured to latch the switch-on signal in response tothe voltage at the voltage-sensing node reaching the threshold.
 12. Thepower supply system of claim 8, further comprising a voltage clampcoupled between a ground node and the voltage-sensing node, wherein thevoltage clamp is configured to clamp to a limit value of the voltage atthe voltage-sensing node.
 13. The power supply system of claim 9,wherein the first electronic switch has a first node configured to becoupled to the high-voltage node and a second node configured to becoupled to the low-voltage circuitry, and wherein the charge pump iscoupled to the current flow path of the first electronic switch at thesecond node.
 14. The power supply system of claim 8, wherein the firstelectronic switch and the second electronic switch are MOSFETtransistors.
 15. A method, comprising: coupling low-voltage circuitry tohigh-voltage source by switching a first electronic switch to aconductive state; coupling a second electronic switch between avoltage-sensing node and the first electronic switch; coupling thevoltage-sensing node to the first electronic switch by switching thesecond electronic switch to a conductive state in response to a voltageat the voltage-sensing node reaching a threshold; moving electric chargefrom a current flow path of the first electronic switch to a controlnode of the first electronic switch by activating a charge pump with thesecond electronic switch after switching the second electronic switch tothe conductive state.
 16. The method of claim 15, comprising: charging acharge capacitor by the charge pump with charge in excess of the chargepumped to the control node of the first electronic switch.
 17. Themethod of claim 15, comprising: pumping, by the charge pump, chargesourced from the current flow path of the first electronic switch to thevoltage-sensing node.
 18. The method of claim 15, comprising: latching,by a latch circuit coupled between a comparator and the secondelectronic switch, a switch-on signal in response to the voltage at thevoltage-sensing node reaching the threshold.
 19. The method of claim 15,comprising: clamping, by a voltage clamp coupled between a ground nodeand the voltage-sensing node, the voltage at the voltage-sensing node toa limit value.
 20. The method of claim 15, comprising: coupling a firstnode of the first electronic switch to a high-voltage node; coupling asecond node of the first electronic switch to the low-voltage circuitry;and coupling the charge pump to the current flow path of the firstelectronic switch at the second node.